Assembly for vibrating a compacting drum of a compacting machine

ABSTRACT

An assembly for vibrating a compacting drum of a compacting machine includes a shaft rotatably mountable to a compacting drum of the compacting machine. The center of mass of the shaft is offset from the geometrical rotation axis of the shaft. An outer eccentric member is arranged outside of the shaft, wherein the center of mass of the outer eccentric member is offset from the geometrical rotation axis of the shaft. The outer eccentric member is displaceably mounted relative to the shaft for adjustment of the eccentricity of the assembly. An extension of the outer eccentric member in a direction parallel with the geometrical rotation axis of the shaft is at least two times an average extension of the outer eccentric member in a radial direction perpendicular to the geometrical rotation axis of shaft such that a mass of the outer eccentric member forms a distributed load along the geometrical rotation axis of the shaft.

BACKGROUND AND SUMMARY

This disclosure relates to an assembly for vibrating a compacting drumof a compacting machine, the assembly comprising a shaft rotatablymountable to a compacting drum of the compacting machine, the centre ofmass of the shaft being offset from the geometrical rotation axis of theshaft, an outer eccentric member being arranged outside of the shaft,and the centre of mass of the outer eccentric member being offset fromthe geometrical rotation axis of the shaft, and the outer eccentricmember being displaceably mounted relative to the shah for adjustment ofthe eccentricity of the assembly. The disclosure also relates to acompacting machine comprising a frame, at least one compacting drumrotatably connected to the frame, as well as the previously mentionedassembly being mounted to the compacting drum.

The disclosure relates to an assembly for vibrating a compacting machinefor compaction of materials, in particular in earthwork and roadconstruction. Document US20040182185A1 shows an adjusting device forregulating the eccentric moment of an eccentric shaft of a roller drum.The shown device shows an inner eccentric shaft being rotationallypowered by a motor and an outer eccentric shaft being, rotatablerelative to the inner eccentric shaft. The outer eccentric shaftcomprises two axially spaced apart eccentric weights that may be usedfor variably adjusting the resulting total mass eccentricity of theassembly. Consequently, desired vibration amplitude may nearly always beselected from a relatively wide range of vibratory amplitudes.

A disadvantage of the solution of D1 is a relatively high power demandof the driving motor.

There is thus a need for an improved assembly for vibrating a compactingmachine removing the above mentioned disadvantage.

It is desirable to provide an assembly for a compacting drum of acompacting machine, where the previously mentioned problem is at leastpartly avoided.

The disclosure concerns an assembly for vibrating a compacting drum of acompacting machine, the assembly comprising a shaft rotatably mountableto a compacting drum of the compacting machine, the centre of mass ofthe shaft being offset from the geometrical rotation axis of the shaft,and an outer eccentric member arranged outside of the shaft, the centreof mass of the outer eccentric, member being offset from the geometricalrotation axis of the shaft, and the outer eccentric member beingdisplaceably mounted relative to the shaft for adjustment of theeccentricity of the assembly

The disclosure is characterized in an extension of the outer eccentricmember in a direction parallel with the geometrical rotation axis of theshaft is at least two times an average extension of the outer eccentricmember in a radial direction perpendicular to the geometrical rotationaxis of shaft such that a mass of the outer eccentric member forms adistributed load along the geometrical rotation axis of the shaft.

The selected relationship between the axial extension of the outereccentric member and the average extension of the outer eccentric memberin a radial direction results in a certain level of axial massdistribution of the outer eccentric member. By distributing the mass ofthe outer eccentric member in the direction of the geometrical rotationaxis of the shaft the assembly, also referred to as axial directionhereinafter, the moment of inertia of the outer eccentric member isreduced. This reduction in moment of inertia is the result of a reduceddistance (D) between the geometrical rotation axis of the outereccentric member and the centre of weight of the outer eccentric memberin a plane perpendicular to the axial direction. The moment of inertia(I) of the outer eccentric member equals the product of the mass (M) andsaid distance (D) squared, i.e I=M×D². Hence, by reducing the distancethe moment of inertia is reduced. A reduced distance between thegeometrical rotation axis of the outer eccentric member and the centreof weight of the outer eccentric member in a plane perpendicular to theaxial direction naturally also results in reduced eccentricity of theouter eccentric, member, where the eccentricity is the product of themass (M) and said distance (D). However, when for example doubling themass (M) and reducing the distance (D) by half, the eccentricity has notchanged but the moment of inertia is reduced due to the squared distance(D²) in the moment of inertia calculation. As a result, by distributingthe mass of the outer eccentric member in the axial direction, themoment of inertia may be reduced while the eccentricity of the outereccentric member is kept constant.

A reduced moment of inertia of the outer eccentric member results in areduced moment of inertia of the complete assembly when nothing else hasbeen changed, and this allows a reduced power output of the motor thatis used for rotating the assembly while the rotational accelerationremains unchanged. A reduced power output demand of the motor allows acorrespondingly smaller motor power, which consequently requires lesspower output of the main power source of the compacting machine. Forexample, a smaller hydraulic motor for powering the eccentric assemblyallows a reduced hydraulic power output of the hydraulic pump drivingthe hydraulic motor. As a result, the main diesel engine powering thehydraulic pump may have a reduced maximal power output, and thus reducedfuel consumption. In all, the solution of the disclosure allows reducedfuel consumption.

Further advantages can be achieved. For example, the extension of theouter eccentric member in the direction parallel with the geometricalrotation axis of the shaft may be at least three times, preferably atleast five times, and more preferably at least ten times the averageextension of the outer eccentric member in the radial directionperpendicular to the geometrical rotation axis of the shaft. A moredistributed load and a shorter radial distance between the load and thecentre of rotation of the shaft results in further reduced moment ofinertia.

The outer eccentric, member may have an extension in the directionparallel with the geometrical rotation axis of the shaft exceeding 10%,preferably exceeding 20%, and more preferably exceeding 50% of theunsupported length of the shaft. As described above, a more distributedload results in that the centre of mass of the eccentric member can belocated closer to the rotational axis of the shaft, and thereby reducingthe moment of inertia for a given mass.

The outer eccentric member may have an extension in the directionparallel with the geometrical rotation axis of the shaft exceeding 10%,preferably exceeding 20%, and more preferably exceeding 50% of thelength of an eccentric mass of the shaft.

The outer eccentric member may exhibit an axial length of at least 100millimeters, preferably at least 150 millimeters, and more preferably atleast 200 millimeters. A distributed load of the eccentric member yieldadvantageous aspects in terms of energy efficiency.

The outer eccentric member may be pivotally mounted relative to theshaft. This arrangement enables a robust design and cost-effectivemanufacturing of the assembly.

The mass of any axial segment of an unsupported axial length of theouter eccentric member may differ less than 75% from the mass of anyother axial segment of the unsupported axial length of the outereccentric member with the same axial length, preferably less than 50%,and more preferably less than 40%. A more evenly distributed mass overthe length of the eccentric member enables reduced moment of inertia ofthe eccentric member.

The mass of the unsupported axial length of the outer eccentric memberis substantially regularly distributed over the unsupported axial lengthof the outer eccentric member. A more evenly distributed mass over thelength of the eccentric member enables reduced moment of inertia of theeccentric member.

The outer eccentric member is attached to the shaft by means of at leasttwo support members, said at least two support members being spacedapart in a direction of the geometrical rotation axis of the shaft andpivotally mounted on the exterior of the shaft. This arrangement enablesa reliable and robust rotatable mounting of the outer eccentric memberto the shaft. The rotatable mounting may be realised by relativelynarrow roller or sliding bearings, thereby enabling low maintenancecosts and high reliability.

Each support member may be formed as an individual member that connectsthe outer eccentric member with the shaft. This design enablescost-effective manufacturing.

One support member may be positioned on each side of an eccentric massof the shaft. This layout enables a robust design.

The outer eccentric member is rotatable relative to the shaft in anangular range that is limited by a first end position at a first end ofthe range and a second end position at a second end of the range, whichangular range is less than 360 degrees, preferably less than 180degrees. 180 degrees appears to represent the largest possibledifference in total assembly eccentricity between the first and secondend positions, where the eccentricity of the shaft and the outereccentric member match in one of said first or second end positions andare opposite each other in the other of said first or second endpositions.

The total centre of mass of the shaft and the outer eccentric member isoffset from the geometrical rotation axis of the shaft with a firstdistance when the outer eccentric member is located in a first endposition, and the total centre of mass of the shaft and the outereccentric member is offset from the geometrical rotation axis of theshaft with a second distance when the outer eccentric member is locatedin a second end position, wherein the first and second distances aredifferent. This arrangement essentially implies that the assemblyexhibits two different levels of eccentricity of the total assemblydepending on the position of the outer eccentric member. This isadvantageous when compacting different types of material and materiallayer thickness, wherein eccentricity oldie total assembly may beselected to best fit the specific situation.

The shaft may comprise a first stop arrangement for preventing relativerotation between the shaft and the outer eccentric member in a firstangular direction at a first end position, and a second stop arrangementfor preventing relative rotation between the shaft and the outereccentric member in a second angular direction, opposite to the firstangular direction, at the second end position. The first and second stoparrangements allow selection of the total assembly eccentricity simplyby means of rotating the shaft in a first direction or a seconddirection. This arrangement enables a particularly robust and reliabledesign of a multi-position eccentric assembly because no moving controland/or actuating members are required to change the eccentricity of theassembly.

The assembly may comprise spring means for damping an impact force thatmay be generated when the outer eccentric member or the support membersis/are brought into contact with the shaft at the first end positionand/or the second end position. When the outer eccentric member islocated in for example the first end position and the shaft suddenly ispowered to rotate in the opposite direction, the outer eccentric memberwill change angular position relative to the shaft to the other endposition. Depending on the acceleration of the shaft, the outereccentric member will arrive at the other end position having angularspeed that is different from the angular speed of the shaft, such that asudden change in angular speed of the outer eccentric member will occur.The moment of inertia in combination with a sudden change in angularspeed may result in a relatively high contact force between the outereccentric member and the shaft, and this force must be absorbed withoutdamaging the assembly. Previously, this was realised by forming theparts of the assembly relatively strong and robust such that the impactforce could be absorbed without damages. However, strong and robustparts imply a high moment of inertia, which implies a relatively highpower output of the motor for rotationally powering the assembly,thereby resulting in high fuel consumption of the compacting machine. Byproviding the assembly with spring means for clamping the impact forcethe parts of the assembly, in particular the shaft and the outereccentric member may be less strong and robust, such that a reducedmoment of inertia results, and thereby also reducing the fuelconsumption.

The spring means may be arranged on the outer eccentric member, inparticular at the end regions of the outer eccentric member.Alternatively, the spring means may be arranged on the shaft, inparticular at the end regions of the shaft. Still alternatively, thespring means may be arranged on one or more of said at least two supportmembers.

The spring means may comprise at least one spring member in form ofhelical spring, disc spring, elastic member, or the like.

The spring means itself may be arranged to directly contact the shaftand the outer eccentric member for absorbing impact energy upon impact.This arrangement corresponds to a relative simple and cost-effectivesolution. Alternatively, the spring means may additionally comprise atleast one abutment member arranged to transfer the impact energy to thespring member. The abutment member may be arranged to prevent damages tothe spring member, and/or simplifying guidance of the spring means forpreventing the spring means from unwanted deformation.

The at least one abutment member may cooperate with guiding means forguiding the at least one abutment member along a path, wherein theguiding means preferably is formed of at least one recess in which theat least one abutment member is at least partly slidingly positioned.Guiding means of the abutment member may enable guidance of the springmeans for preventing the spring means from unwanted deformation.

The at least one spring member may be installed in a preloaded state,i.e in a compressed state. This arrangement enables a higher dampingforce from the very beginning of the motion path upon impact, andprevents loose parts in the assembly. The preloaded spring member mayalso enable a preloaded mounting of the outer eccentric member withinthe support members.

The at least one recess may be a through-hole, a first abutment membermay be arranged at a first end of the through-hole, a second abutmentmember may be arranged at a second end of the through-hole, and thespring member may be arranged between the first and second abutmentmember. This arrangement allows damping means being located on bothsides of a member, such as the outer eccentric member of support member.Hence, a single recess and a single spring member may be used forrealising damping means on both sides of the member, thereby reducingcosts.

The spring means may be positioned in a central region of the outereccentric member and/or the shaft. This arrangement results in lessspring means, thereby reducing cost. For example, the outer eccentricmember may be constituted by at least one leaf spring, and the shaft maycomprise at least one abutment surface positioned in a central region ofthe shaft, and the leaf spring may be arranged to interact with theabutment surface for damping the impact force.

The outer eccentric member may be constituted by at least one leafspring, and the shaft comprises at least one projecting abutment memberpositioned in a central region of the shaft, and the leaf spring isarranged to interact with the projecting abutment member for damping theimpact force. This arrangement defines an alternative solution fordamping the impact force.

The outer eccentric member lay be constituted by at least one metal barthat is fastened to the at least two support members. This arrangementenables a cost-effective solution.

The outer eccentric, member may be constituted by at least two metalbars that are inserted in a recess in at least two support members, andthe at least two metal bars are fastened to each of the support membersby means of spring means that presses apart the at least two metal bars,such that each of at least two metal bar abuts an opposing inner surfaceof the recess of the at least two support members. This arrangementenables a rattle-free and fast mounting of the outer eccentric member,thereby simplifying manufacturing of the assembly.

The shaft may over a majority of its axial extension have substantiallya cross-sectional circular segment shape in a plane perpendicular to thegeometrical rotation axis of the shaft, wherein the circular segment hasa central angle of more than 90 degrees, and preferably more than 120degrees. It has been found that the shaft is provided with aparticularly low moment of inertia in combination with a higheccentricity when the shaft and outer eccentric member jointly exhibitsa circular cross-sectional area in a plane perpendicular to the axialdirection, wherein a periphery of the circle crosses the geometricalcentre of rotation of the shaft.

A majority of the mass of the outer eccentric member in a first endposition may be located inside a geometrical cross-sectional circle in aplane perpendicular to the geometrical rotation axis of the shaft, whichcircle has the same centre and same radius as the circular segment. Asmentioned above, it has been found that the shaft is provided with aparticularly low moment of inertia in combination with a higheccentricity when the shaft and outer eccentric member jointly exhibitsa circular cross-sectional area in a plane perpendicular to the axialdirection, wherein a periphery of the circle crosses the geometricalcentre of rotation of the shaft.

The geometrical rotation axis of the shaft may be positioned within, onor outside a geometrical cross-sectional circle in a plane perpendicularto the geometrical rotation axis of the shaft, which circle has the samecentre and same radius as the circular segment.

The geometrical cross-sectional circle extends within a distance fromthe geometrical rotation axis of the shaft, which distance is in therange of 0-50 millimeters, preferably 0-25 millimeters, and morepreferably 0-10 millimeters. As mentioned above, it has been found thatthe shaft is provided with a particularly low moment of inertia incombination with a high eccentricity when the shaft and outer eccentricmember jointly exhibits a circular cross-sectional area in a planeperpendicular to the axial direction, wherein a periphery of the circlecrosses the geometrical centre of rotation of the shaft. However, alsowhen the periphery of the circle is located relatively close to thecentre of rotation a significant reduction in moment of inertia isachieved.

Each support member may be formed by a connecting rod. This enables areduced moment of inertia.

The shaft may be a solid shaft. A solid shaft without an internal cavityenables a reduced moment of inertia of the assembly.

The disclosure also relates to a compacting machine that comprises aframe and at least one compacting drum according to the disclosurerotatably connected to the frame.

The compacting machine may further comprise a motor for rotationallydriving the assembly in any rotational direction, wherein the assemblymay be rotationally mounted in two spaced apart parallel supports thatare fastened to an interior wall of the compacting drum, which supportsare configured to transfer vibrations generated by the assembly to thecompacting drum.

BRIEF DESCRIPTION OF DRAWINGS

In the detailed description of the disclosure given below reference ismade to the following figure, in which:

FIG. 1 shows a compacting machine;

FIG. 2 shows a cross-sectional view of a compacting drum comprising anassembly for vibrating the machine;

FIG. 3 shows a front perspective view of the assembly for vibrating themachine;

FIG. 4 shows a rear perspective view of the assembly for vibrating themachine;

FIG. 5 shows a cross-sectional view in an axial direction of theassembly;

FIG. 6 shows a detailed solution of spring means for damping an impactforce; and

FIG. 7 shows an alternative embodiment of the assembly.

DETAILED DESCRIPTION

Various aspects of the disclosure will hereinafter be described inconjunction with the appended drawings to illustrate and not to limitthe disclosure, wherein like designations denote like elements, andvariations of the disclosed aspects are not restricted to thespecifically shown embodiments, but are applicable on other variationsof the disclosure.

Vibratory steel drums exert forces which increase compactive effort.Vibratory drums have internal eccentric weights that rotate on a shaft.The rotating eccentric weight causes the drum to move in all directionsbut the effective part is the up and down movement. Vibratory forces arethe rapid up and down movements which cause aggregates and soilparticles to move. Aggregates in motion tend to re-orient themselveseasier so the material compacts easier under the weight of the drum.Vibration is a particularly effective tool for the aggregate orparticulate material like sand and gravel. A relatively large compactingmachine typically comprises a frame, a front compacting drum and a rearcompacting drum rotatable connected to the frame. The machine mayfurther comprise a motor for rotationally driving, an assembly forvibrating the compacting machine, and in particular for vibrating thefront and/or rear compacting drum. The machine may have a static weightof about 10 000 kg, such that each drum exerts a static weight of about5000 kg. In addition to the static weight, each vibratory drum may exerta dynamic weight of about 12 000 kg merely caused by the centrifugalforces generated by an eccentric rotating assembly positioned withineach vibratory compacting drum. Hence, to total effective compactingweight may typically add up to about 17 000 kg. This example clearlyshows the advantage of providing the compacting drum with a rotatingvibratory assembly.

FIG. 1 shows a tandem compaction machine 1 that comprises a frame 2 withdriver's cab 3, a front compacting drum 4 and a rear compacting drum 5each being mounted via a steerable swivel coupling 6, 7 at the front andrear underneath said frame 2 respectively. Situated between the twocompacting drums 4, 5 is an engine compartment 8 which houses a driveengine, usually a diesel engine. Although the disclosure is focused on acompaction machine having two compacting drums and a driver's cabin, thedisclosure is equally applicable to compacting machines having a singlecompacting drum and/or compacting machines that are pulled or pushed byother objects, such as a tractor or a human operator.

FIG. 2 shows a schematic and simplified cross-sectional view of one ofthe compacting drums 4, 5. The compacting drum 4, 5 comprises acylindrical wall 20 that contacts the ground. The cylindrical wall 20 isconnected to structural support plates 23 and rotatable mounted by meansof two outer radially extending plates 21. The radially extending plates21 are mounted to the structural support plates 23 via vibration dampingelements 25, such as rubber-metal elements. A motor 35, such ashydraulic motor or hydraulic motor combined with a gearbox, is fastenedto a frame support member 24 to drive the compacting drum 4, 5 of thecompaction machine 1. Bearings 22 are integrated into motor 15 andradially extending plate 21 to allow rotation of the radially extendingplates 21 and the cylindrical wall 20 relative to frame support 24 todrive the compaction machine 1.

Situated in the centre of the compacting drum 4, 5 is an assembly 30 forvibrating a compacting machine. A rotatable shaft 26 of the assembly 30is driven by a motor 27, such as a hydraulic or electric motor, via adriving shaft 28. The shaft 26 being rotatable supported by bearings 29positioned near end portions of the shaft 28 and axially spaced apartwith a distance L4. The unsupported length L4 of the shaft 26corresponds thus to the axial length L4 of the shaft 26 between thecentre of the shaft bearings 29 positioned closest to, and on each sideof an eccentric mass of the shaft 26 The driving shaft 28 beingconnected by means of articulated joints at both ends for allowing thecompacting drum 4, 5 to vibrate with a certain amplitude and frequency.A cylindrical wall 31 being mounted surrounding the assembly 30 andforming a lubrication oil reservoir 33 together with two inner radiallyextending support plates 34, which are in contact with the cylindricalwall 20 and is arranged to transfer vibrations generated by the assembly30 to the cylindrical wall 20. A splash pin 32 is provided on the shaft26 and the splash pin 32 and oil fill level are jointly adapted togenerate a lubrication oil mist within the reservoir 33 but with onlythe splash pin 32 being in contact with the liquid, lubrication.

The assembly 30 for vibrating the compacting machine 1 is shown more indetail in FIGS. 3-6. The assembly 30 is arranged to be mounted within atleast one compacting drum 4, 5 of the compacting machine and to generatevibrations that are transferred to the cylindrical outer wall 20 of thecompacting drum 4, 5. The assembly 30 comprises a shaft 26 that isrotatably mountable to the compacting drum 4, 5, and the centre of massof the shaft 26 is offset from the geometrical rotation axis of theshaft 26. The assembly 30 further comprises an outer eccentric member 40being arranged outside of the shaft 26, i.e on the exterior of the shaft26. The centre of mass of the outer eccentric member 40 is offset fromthe geometrical rotation axis of the shaft 26. The outer eccentricmember 40 is displaceably mounted relative to the shaft 26, inparticular pivotally mounted relative to the shaft 26, for adjustment ofthe eccentricity of the assembly. The outer eccentric member 40preferably pivots around the centre of rotation of the shaft 26, but theouter eccentric member 40 may alternatively pivot around an axisradially offset from the centre of rotation of the shaft 26. The total,i.e combined centre of mass of the shaft 26 and the outer eccentricmember 40 may thus be continuously variable in a certain range merely bychanging the internal angular relationship between the shaft 26 andouter eccentric member 40.

Moreover, by rotating the assembly 30 vibrations are generated due tothe eccentric centre of mass of the assembly 30. The vibrations arecaused by the centrifugal force F_(c) which is generated by theeccentric centre of mass upon rotation of the shaft 26, and iscalculated by F_(c)=D×M×ω², where F_(c) denotes centrifugal force inNewton, D denotes distance between centre of rotation and centre of massof the rotating assembly 30, M denotes the total mass in kg of therotating assembly 30, and ω² denotes squared angular velocity inradians/second. The product of the mass M and distance D is sometimesreferred to as the unbalance of the construction. The compacting drum 4,5 will exhibit a circular oscillation motion when the assembly 30 isrotated. The amplitude and frequency of the oscillation motion beingdependent on the rotating speed of the assembly 30 and the generatedcentrifugal force F_(c).

The extension of the outer eccentric member 40 in a direction parallelwith the geometrical rotation axis of the shaft 26 is at least two timesthe extension of the outer eccentric member 40 in a radial directionperpendicular to the geometrical rotation axis of shaft 26. Thisrelationship is selected to ensure that the mass of the outer eccentricmember 40 forms a distributed load along, the geometrical rotation axisof the shaft 26, whereby it is assumed that the mass of the eccentricmember 40 is distributed more or less evenly over the axial length ofthe eccentric member 40. The distributed load and the geometrical formof the assembly 30 aims at achieving a low moment of inertia whilehaving a sufficiently high level of unbalance, as described above. Anassembly having for example one or two eccentric weights each acting asa point load results in a higher moment of inertia, and requirestherefore higher power output of the assembly driving motor 27 foraccelerating the assembly 30 with a similar acceleration.

FIG. 3 and FIG. 4 shows a first embodiment of the assembly 30 from afront and back perspective view respectively. The extension of the outereccentric member 40 in a direction parallel with the geometricalrotation axis of the shaft 26 is referred to as L₃ in FIG. 4, andrepresents the maximal axial extension of the eccentric member 40. Theaverage extension of the outer eccentric member 40 in a radial directionis defined as the average distance from a centre of rotation of theshaft 26 to the maximal radial extension of the eccentric member 40 overthe axial length of the eccentric member 40. The shaft 26 is solid andmay for example be made of cast metal. The shaft 26 comprises bearingsupport surfaces 41 at axial end regions of the shall 26. The bearingsupport surfaces 41 carries, when assembled in a compacting drum, shallbearings that enable rotatable mounting of the shaft 26 in thecompacting drum 4, 5. The shaft 26 is thus freely rotatable within thedrum 4, 5. An eccentric mass 42 is integrally provided at a centralregion of the shaft 26. The eccentric mass is axially distributed over alength which is preferably positioned centred with respect to the axialextension L₃ of the outer eccentric member 40. For example, the axialextension of the eccentric mass 42 of the shaft 26 may be at least 100millimeters, preferably at least 150 millimeters, and more preferably atleast 200 millimeters. Furthermore, the axial extension l_i of theeccentric mass 42 of the shaft 26 may correspond to at least 15% of thetotal length l_2 of the shaft 26, preferably at least 35% of the totallength L₂ of the shaft 26, and more preferably at least 55% of the totallength L₂ of the Shaft 26. The total length l_2 of the shaft 26 ismeasured in the axial direction of the shaft and corresponds to thelength of the shaft 26 as a single piece. Additional shafts connected tothe shaft 26, such as driving shaft 28, are not included when measuringthe length of the shaft 26.

The outer eccentric member 40 is rotatable relative to the shaft 26 inan angular range that is limited by a first end position at a first endof the range and a second end position at a second end of the range. Theangular range is less than 360 degrees, and preferably less than about200 degrees for accomplishing a large difference in eccentricity of theassembly 30 between the first and second end positions. The angularrange is preferably also not too large since the impact force then riskto be higher because the shaft 26 may accelerate for a longer timeperiod before the first or second end position is reached, such that theshaft 26 potentially will have a higher angular velocity at the time ofimpact. High impact forces are negative because they may damage theassembly 30. An angular range of about 130-160 degrees may besufficient. As a result of the first and second end positions within arange less than 360 degrees the outer eccentric member will alwaysrotate with the shaft 26 after a rotation of the shaft 26 in a singledirection for more than 360 degrees.

The shaft 26 comprises a first stop arrangement for preventing relativerotation between the shaft 26 and the outer eccentric member 40 in afirst angular direction at the first end position, and a second stoparrangement for preventing relative rotation between the shaft 26 andthe outer eccentric member 40 in a second angular direction, opposite tothe first angular direction, at the second end position. In FIGS. 3 and4, the outer eccentric member 40 is positioned in the first endposition, in which a substantially flat contact surface 43 of the shaft26 forms the first stop arrangement and functions as abutment surface ofthe shaft 26 in the first end position of the outer eccentric member 40.The shaft 26 further comprises two projecting abutment members 44positioned axially spaced apart. The two projecting abutment members 44form the second stop arrangement and function as abutment surfaces ofthe shaft 26 in the second end position of the outer eccentric member40. The second end position is illustrated by the dash-dotted view ofthe outer eccentric member 40 in FIG. 3. The two projecting abutmentmembers 44 are formed integrally with the shaft 26 and positioned suchthat they engage axial side portions of the outer eccentric member 40during contact.

The outer eccentric, member 40 is attached to the shaft 26 by means oftwo support members 45, which are spaced apart in the axial directionand pivotally mounted on the exterior side of the shaft 26, inparticular on the cylindrical end regions 41 of the shaft 26. The spacedapart positioning of the two support members 45 ensures that the mass ofthe outer eccentric member 40 forms a distributed load and not a pointload. For example, the axial extension L₃ of the outer eccentric member40 may be larger than 100 millimeters, preferably larger than 150millimeters, and more preferably larger than 200 millimeters.Furthermore, the extension L of the outer eccentric member 40 in thedirection of the geometrical rotation axis of the shaft corresponds toat least 20% of the total length l_2 of the shaft in the direction ofthe geometrical rotation axis of the shaft, preferably at least 40% ofthe total length L₂ of the shaft 26, and more preferably at least 60% ofthe total length l_2 of the shaft 26. The axial segment of the eccentricmember 40 that is not directly support by the support members 45, i.elocated between the support members 45 is hereinafter referred to as anunsupported axial length of the outer eccentric member 40 andcorresponds in the embodiment of FIG. 2 to the distance Each of thesupport members 45 has preferably the shape of a connecting rod. Thisshape contributes to the eccentricity of the outer eccentric member 40.

The outer eccentric member 40 may be fastened to two support members 45in a variety of ways, such as welding or by fasteners, but a positiveinterlocking of the outer eccentric member 40 and the support members 45is advantageous from a safety aspect. In the embodiment of FIGS. 3 and4, each of the support members 45 is provided with recess 46 orthrough-hole, in which the outer eccentric member 40 may be inserted andsecured. In the specific embodiment shown, the outer eccentric member 40is constituted by two metal bars 40 a, 40 b that are inserted in therecess 46 of each support member 45. The two metal bars 40 a, 40 b arefastened to each of the support members 45 by means of preloaded springmeans 47 that presses apart the two metal bars 40 a, 40 b, such thateach of the two metal bars 40 a, 40 b abuts an opposing inner surface ofthe recess 46 of the two support members 45. This specific solutionenables a Gist assembly of the outer eccentric member 40 to the supportmembers 45, namely by pressing the two bars 40 a, 40 b together,inserting the end thereof into the recess 46 and allowing the bars 40 a,40 b to separate and contact opposite surfaces of the recess 46 underthe force of the still compressed spring means 47. FIG. 5 shows across-section of the spring means 47 of this embodiment in combinationwith abutment members 48, which will be described more in detail below.The spring means 47 is here a plurality of stacked spring discs, butother solutions are possible, such as one or more helical springs,elastic materials, etc. The outer eccentric member 40 is formed of oneor more parts that jointly form a single united member.

From the description above, it is clear that the outer eccentric member40 has two stable positions. The first end position, as illustrated withsolid lines in FIG. 5, and the second end position, as illustrated withthe dash-dotted view of the bars 40 a, 40 b in FIG. 5. Typically, theangular rotatable range 56 of the outer eccentric member is about 90-135degrees. The outer eccentric member 40 will swing to the first or secondend position upon rotation of the shaft 26 in a specific direction bymeans of the motor 27. If the outer eccentric member 40 initially hangsfreely inbetween the first and second end positions and the shaft 26 isnot rotating, and the motor 27 starts to rotate the shaft 26 in a firstdirection A, as illustrated in FIG. 3, then the outer eccentric member40 after a short rotation of the shaft 26, i.e less than 180 degrees,will contact the substantially flat contact surface 43 of the first stoparrangement. This contact position corresponds to the first end positionof the outer eccentric member 40. However, if the motor 27 starts torotate the shaft 26 in a second direction B, then the outer eccentricmember 40 after a short rotation of the shaft 26 will contact the twoprojecting abutment members 44 of the second stop arrangement. Thiscontact position corresponds to the second end position of the outereccentric member 40. After the outer eccentric member 40 has reached andsettled at the first or second end position and the shaft 26 continuesrotating with a minimum speed, then the outer eccentric member 40 willremain at said position. However, if the shaft 26 begins to decelerateor if the rotational velocity of the shaft 26 is too low then the outereccentric member 40 will not remain at the end position. Normally, themotor 27 is set to rotate the shaft 26 with a fixed speed of about1000-4000 rpm, and preferably about 2000-3000 rpm. With such highangular velocity the outer eccentric member 40 will remain fixed at anyend position depending on the angular direction of the shaft 26.

The total centre of mass of the shaft 26 and the outer eccentric member40 is offset from the geometrical rotation axis of the shaft 26 with afirst distance when the outer eccentric member 40 is located in a firstend position, and the total centre of mass of the shaft 26 and the outereccentric member 40 is offset from the geometrical rotation axis of theshaft 26 with a second distance when the outer eccentric member 40 islocated in a second end position, wherein the first and second distancesare different. The assembly 30 may thus be set to generate vibrationswith two different amplitudes depending on the direction of rotation ofthe shaft 26, given a fixed rotation speed of the shaft 26. The twopredetermined vibration modes may be selected by an operator of thecompacting machine by selector means, such as a selector button, touchscreen, or the like, installed in the cab.

The operator may thus select between for example a strong and finevibration mode, or vibration-less operating mode. In the strongvibration mode, the shaft 26 in rotated in direction A, the outereccentric member 40 is positioned in the first end position, in whichthe centre of mass of the shaft 26 and the centre of mass of the outereccentric member 40 are relatively close, i.e with a relatively smallangular distance. The total centre of mass of the assembly 30 is therebyrelatively largely offset from the geometrical axis of rotation of theshaft 26, such that high amplitude oscillations are generated. In thefine vibration more, the shaft 26 in rotated in direction B, the outereccentric member 40 is positioned in the second end position, in whichthe centre of mass of the shaft 26 and the centre of mass of the outereccentric member 40 are relatively spread apart, i.e with a relativelylarge angular distance, typically more than 90 degrees. The total centreof mass of the assembly 30 is thereby less offset from the geometricalaxis of rotation of the shaft 26, such that low amplitude oscillationsare generated. The operator may select if vibration mode should be used,and what vibration mode is deemed suitable. Typically, the drum 4, 5oscillates with about 1 millimeter, i.e has an amplitude of about amillimeter when the strong vibration mode is selected. This vibrationmode is typically used for compacting thicker layers of material.Similarly, the drum 4, 5 oscillates with about 0.5 millimeters when thefine vibration mode is selected. This vibration mode is typically usedfor compacting thinner layers of material.

It has been found that an optimal combination of low moment of inertiaand high eccentricity of the assembly may be attained m an end positionof the outer eccentric member 40 when shaping the shaft 26 and outereccentric member 40 such as to jointly form a circular cylinder that ispositioned with its axis parallel with axis of the assembly 30, and withits cylindrical surface passing through the geometrical centre ofrotation of the shaft 26. This shape is however difficult to attain dueto dimensional and manufacturing cost limitations of the shaft 26 andouter eccentric member 40. FIG. 5 shows a cross-section of the assembly30 in a plane perpendicular to the axial direction, where the outereccentric member 40 and shaft 26 have been funned to approach thecombined shape that is deemed to be optimal. Here the shaft 26 over amajority of its axial extension has substantially a cross-sectionalcircular segment shape, wherein the circular segment 54 has a centralangle 52 of more than 90 degrees, and preferably more than 120 degrees.A larger circular segment 54 corresponds to a better conformity to thedesired cylindrical shape. Furthermore, a majority of the mass of theouter eccentric member 40 in the tint end position is located inside thegeometrical cross-sectional circle 53 in a plane perpendicular to thegeometrical rotation axis of the shaft 26, which circle 53 has the samecentre 55 and same radius as the circular segment 54. The radially innerlongitudinal portion of the outer eccentric member 40 is even chamferedto better conform to the shape of the shaft 26 as well as to the shapeof the geometrical cross-sectional circle. The shape of the shaft 26 andouter eccentric member 40 may of course be shaped to even better jointlyconform to the geometrical cross-sectional circle but to a highmanufacturing cost. The disclosed form represents a good compromise oflow manufacturing costs and high conformity to the desired geometricalcross-sectional circle, in the disclosed embodiment of FIG. 5, thegeometrical cross-sectional circle 53 passes through the centre ofrotation of the shaft 26, but the circle may alternatively pass insideor outside the centre of rotation offset with a distance in the range of0-50 millimeters, preferably 0-25 millimeters, and more preferably 0-10millimeters.

Depending on the acceleration or deceleration of the shaft 26 and theweight of the outer eccentric member 40 a more or less strong impactwill occur when the outer eccentric member 40 engages the first andsecond stop arrangement of the shaft 26. This sudden impact may thusresult in relatively large impact forces that must be absorbed b theparts 27, 40, 45, and this may lead to damages to the assembly 30. Onesolution for preventing damages is to make the shaft 26 and outereccentric member 40 relatively massive for withstanding elevated impactforces. Massive parts of the assembly 30 however results in increasedmoment of inertia and therefore increased fuel consumption. A solutionthat does not require massive dimensions of the assembly is thusdesired. The assembly of the present disclosure therefore comprisesspring means for damping an impact force that is generated when theouter eccentric member 40 is brought into contact with the shaft 26 atthe first end position and the second end position. The spring means isthus arranged to absorb at least part of the impact force.

FIG. 6 shows a detailed solution for accomplishing damping of impactforces according to the first embodiment of the disclosure. Here thespring means 47 is arranged at the end regions of the outer eccentricmember 40 in locations that correspond to the locations of the twoprojecting abutment members 44. Two spaced apart impact locations allowthe impact force to be divided between the two impact locations. Theimpact damping means is here combined with the fastening means of theouter eccentric member 40 to the support members 45 for reducing numberof parts of the assembly 30. The spring means 47 comprises a pluralityof spring members in form of stacked disc springs that are preloadedarranged between two abutment members 48 that are arranged to transferthe impact force to the spring member. The spring members themselvestherefore do not contact the shaft 26 in this embodiment. The abutmentmembers 48 are positioned in a through-hole 49 in the outer eccentricmember 40 and prevented from escaping by means of a flange of the outereccentric member 40 that engage a flange of the abutment member 48. Twosuch abutment members 48 are installed in the outer eccentric member 40facing opposite directions, and the spring members are securely locatedwithin the through-hole 49 between the two abutment members 48. Acentral common guidance pin 50 is also slidingly provided centrallywithin the abutment members 48 for together with the through-hole 49form guiding means that prevent the abutment members 48 from tiltinginside the through-hole 49. The preloaded spring members ensure that theabutment members 48 are always in a protruding position when innon-contact state. The abutment members 48 are arranged to abut eitherthe flat contact surface 43 of the first stop arrangement, as shown inFIG. 6, or the two projecting abutment members 44 of the second stoparrangement.

The spring means 47 may alternatively be formed without abutment members48 and with the spring member itself contacting the shaft 26(non-showed). The spring means 47 may still alternatively be positionedon the shaft 26 (non-showed), preferably at locations of the shaft 26that corresponds to the end regions of the eccentric assembly 30. Stillmore alternatively, the spring means 47 may be arranged on one or bothof the support members 45 (non-showed). Still more alternatively, thespring means 47 may comprise one or more elastic damping member(non-showed) that functions as impact damper. The elastic damping memberdoes not even require a recess but may be secured to the outer surfaceof at least one of the outer eccentric member 40, shaft 26 or supportmembers 45 by adhesive, threaded members, riveting, or the like.

Furthermore, the spring means 47 may still alternatively be positionedin a central region of the outer eccentric member 40 and/or the shaft26. This may reduce the lumber of spring means installations, and theshaft 26 may then be provided with a single centrally positionedprojecting abutment member 44. FIG. 7 shows an embodiment having singlecentrally positioned projecting abutment member 44. The spring means 47is here constituted by the outer eccentric member 40 itself, which isformed of one or more leaf springs that are fastened to the supportmembers 45 and arranged to interact with the centrally positionedprojecting abutment member 44 for damping the impact force. Acorresponding centrally positioned projecting abutment surface 57 may beprovided on the flat abutment surface 43. The spring means 47 mayalternatively be formed by centrally arranged separate spring memberswith or without abutment members, similar to previously shown solutions.

The detailed disclosure involves a few variations in design but manymore variations are included in the scope of protection as defined bythe claims. The outer eccentric member 40 and/or shaft 26 may forexample be formed by single or multiple parts and their shape may bemodified to better conform to the geometrical circle passing through thecentre of rotation. More than two rotatable support members 45 may alsobe used for securing the outer eccentric member 40 to the shaft 26.

Reference signs mentioned in the claims should not be seen as limitingthe extent of the matter protected by the claims, and their solefunction is to make claims easier to understand. As will be realised,the disclosure is capable of modification in various obvious respects,all without departing from the scope of the appended claims.Accordingly, the drawings and the description thereto are to be regardedas illustrative in nature, and not restrictive.

The invention claimed is:
 1. An assembly for vibrating a compacting drumof a compacting machine, the assembly comprising a shaft rotatablymountable to a compacting drum of the compacting machine, the centre ofmass of the shaft being offset from the geometrical rotation axis of theshaft, and an outer eccentric member separate from the shaft, the centreof mass of the outer eccentric member being offset from the geometricalrotation axis of the shaft, and the outer eccentric member beingdisplaceably mounted relative to the shaft for adjustment of theeccentricity of the assembly, wherein an extension of the outereccentric member in a direction parallel with the geometrical rotationaxis of the shaft is at least two times an average extension of theouter eccentric member in a radial direction perpendicular to thegeometrical rotation axis of the shaft, such that a mass of the outereccentric member forms a distributed load along the geometrical rotationaxis of the shaft, wherein the shaft comprises a first stop arrangementfor preventing relative rotation between the shaft and the outereccentric member in a first angular direction at a first end position,and a second stop arrangement for preventing relative rotation betweenthe shaft and the outer eccentric member in a second angular direction,opposite to the first angular direction, at the second end position. 2.An assembly according to claim 1, wherein the extension of the outereccentric member in the direction parallel with the geometrical rotationaxis of the shaft is at least three times the average extension of theouter eccentric member in the radial direction perpendicular to thegeometrical rotation axis of the shaft.
 3. An assembly according toclaim 1, wherein the outer eccentric member has an extension in thedirection parallel with the geometrical rotation axis of the shaftexceeding 10% of an unsupported length of the shaft.
 4. An assemblyaccording to claim 1, wherein the outer eccentric member has anextension in the direction parallel with the geometrical rotation axisof the shaft exceeding 10% of the length of an eccentric mass of theshaft.
 5. An assembly according to claim 1, wherein the outer eccentricmember being pivotally mounted relative to the shaft.
 6. The assemblyaccording to claim 1, wherein the outer eccentric member exhibits anaxial length of at least 100 millimeters.
 7. The assembly according toclaim 1, wherein the mass of any axial segment of an unsupported axiallength of the outer eccentric member differs less than 75% from the massof any other axial segment of the unsupported axial length of the outereccentric member with the same axial length.
 8. The assembly accordingclaim 1, wherein the mass of an unsupported axial length of the outereccentric member is substantially regularly distributed over theunsupported axial length of the outer eccentric member.
 9. The assemblyaccording to claim 1, wherein the outer eccentric member is attached tothe shaft by means of at least two support members, the at least twosupport members being spaced apart in a direction of the geometricalrotation axis of the shaft and pivotally mounted on the exterior of theshaft.
 10. The assembly according to claim 9, wherein each supportmember is formed as an individual member that connects the outereccentric member with the shaft.
 11. The assembly according to claim 9,wherein one support member is positioned on each side of an eccentricmass of the shaft.
 12. The assembly according to claim 1, wherein theouter eccentric member is rotatable relative to the shaft in an angularrange that is limited by a first end position at a first end of therange and a second end position at a second end of the range, whichangular range is less than 360 degrees.
 13. The assembly according toclaim 1, wherein the total centre of mass of the shaft and the outereccentric member is offset from the geometrical rotation axis of theshaft with a first distance when the outer eccentric member is locatedin a first end position, and the total centre of mass of the shaft andthe outer eccentric member is offset from the geometrical rotation axisof the shaft with a second distance when the outer eccentric member islocated in a second end position, wherein the first and second distancesare different.
 14. A compacting machine comprising a frame and at leastone compacting drum rotatably connected to the frame, wherein theassembly of claim 1 is mounted to the at least one compacting drum. 15.The compacting machine according to claim 14, further comprising a motorfor rotationally driving the assembly in any rotational direction,wherein the assembly is rotationally mounted in two spaced apartparallel supports that are fastened to an interior surface of acylindrical wall of the compacting drum, which supports are configuredto transfer vibrations generated by the assembly to the cylindricalwall.
 16. The assembly according to claim 1, wherein the assemblycomprises spring means for damping an impact force that may be generatedwhen the outer eccentric member reaches the first end position and/orthe second end position.
 17. The assembly according to claim 16, whereinthe spring means is arranged on the outer eccentric member.
 18. Theassembly according to claim 17, wherein the spring means is arranged atthe end regions of the outer eccentric member.
 19. The assemblyaccording to claim 16, wherein the spring means is arranged on theshaft.
 20. The assembly according to claim 19, wherein the spring meansis arranged at the end regions of the shaft.
 21. The assembly accordingto claim 9, wherein the assembly comprises spring means for damping animpact force that may be generated when the at least two support membersare brought into contact with the shaft at the first end position and/orthe second end position, wherein the spring means is arranged on one ormore of the at least two support members.
 22. The assembly according toclaim 16, wherein the spring means comprises at least one spring memberin form of helical spring, disc spring, spring washer, elastic member,or the like.
 23. The assembly according to claim 16, wherein the springmeans additionally comprises at least one abutment member arranged totransfer the impact force to the spring member.
 24. The assemblyaccording to claim 23, wherein the at least one abutment membercooperates with guiding means for guiding the at least one abutmentmember along a path, wherein the guiding means is formed of at least onerecess in which the at least one abutment member is at least partlypositioned.
 25. The assembly according to claim 22, wherein the at leastone spring member is preloaded.
 26. The assembly according to claim 24,wherein the at least one recess is a through-hole, a first abutmentmember is arranged at a first end of the through-hole, a second abutmentmember is arranged at a second end of the through-hole, and the springmember is arranged between the first and second abutment member.
 27. Theassembly according to claim 16, wherein the spring means is positionedin a central region of the outer eccentric member and/or the shaft. 28.The assembly according to claim 1, wherein the outer eccentric member isconstituted by at least one leaf spring, and the shaft comprises atleast one projecting abutment member positioned in a central region ofthe shaft, and the leaf spring is arranged to interact with theprojecting abutment member for damping the impact force.
 29. Theassembly according to claim 9, wherein the outer eccentric member isconstituted by at least one metal bar that is fastened to the at leasttwo support members.
 30. The assembly according to claim 9, wherein theouter eccentric member is constituted by at least two metal bars thatare inserted in a recess in at least two support members, and the atleast two metal bars are fastened to each of the support members bymeans of spring means that presses apart the at least two metal bars,such that each of at least two metal bar abuts an opposing inner surfaceof the recess of the at least two support members.
 31. The assemblyaccording to claim 1, wherein the shaft over a majority of its axialextension has substantially a cross-sectional circular segment shape ina plane perpendicular to the geometrical rotation axis of the shaft,wherein the circular segment has a central angle of more than 90degrees.
 32. The assembly according to claim 31, wherein a majority ofthe mass of the outer eccentric member in a first end position islocated inside a geometrical cross-sectional circle in a planeperpendicular to the geometrical rotation axis of the shaft, whichcircle has the same centre and same radius as the circular segment. 33.The assembly according to claim 31, wherein the geometrical rotationaxis of the shaft is positioned within, on or outside a geometricalcross-sectional circle in a plane perpendicular to the geometricalrotation axis of the shaft, which circle has the same centre and sameradius as the circular segment.
 34. The assembly according to claim 32,wherein the geometrical cross-sectional circle extends within a distancefrom the geometrical rotation axis of the shaft, which distance is inthe range of 0-50 millimeters.
 35. The assembly according to claim 9,wherein the each support member has the shape of a connecting rod. 36.The assembly according to claim 1, wherein the shaft is solid.